Due to the inherent intermittency of solar energy, photovoltaic (PV) microinverters (MIs) often operate under prolonged light-load conditions. To improve energy utilization, this paper proposes a novel online iterative trajectory optimization (OITO) strategy for the single-stage series resonant dual-active-bridge (DAB) MI to enhance the light-load efficiency. Through the zero-voltage switching (ZVS) condition analysis, the all-switch ZVS constraint is constructed. On this basis, a ZVS-constraine